Gels and processes for producing them, are well known. As used herein the term "gel" encompasses aerogels, xerogels, hydrogels and other gels known in the art. The term "aerogel" was coined by S. S. Kistler in U.S. Pat. No. 2,188,007 and is generally utilized to refer to a gel which has been dried under supercritical temperature/pressure conditions. Gels, in particular aerogels, are utilized in a wide variety of applications, including thermal and acoustic insulation, catalyst supports and carriers, filters and molecular sieves and electronics.
Gels having lower bulk densities are more advantageous for use in many applications. Because of their lower bulk densities, aerogels have become the gel of choice for many applications. However, as set forth above, aerogels are typically produced utilizing supercritical drying, which requires the use of relatively expensive processing equipment and conditions.
It is also advantageous for certain applications, such as adsorbents to use gels having higher bulk densities.